1. Field of the Invention
The invention relates to the field of light emitting diodes, and preferably high-power laser diodes, designed to equip, for example, illumination systems mounted on motor vehicles. These diodes make it possible to produce beams of which the form and distribution of light can be modulated as required.
2. Description of the Related Art
Such devices are described, by way of example, in publication EP 2 063 170 and publication EP 2 690 352. However, these diodes have to be associated with an effective cooling device owing to the large amounts of heat they produce.
To that end, it has been proposed to mount the diodes on supports acting as radiators, allowing the diode to be assembled into the illumination system.
To optimize the orientation of the light beam emitted by the diode, the optical device in which the diode is mounted has to be adjusted in advance and the angular position of the diode about its central axis, passing substantially through the center of the part of the light-emitting diode, has to be precisely positioned so as to optimize the light yield of the device.
The diode is then turned about the central axis until this optimal position is achieved.
The connection or joining pins used to power and to control the diode are arranged, generally speaking, on the rear part of the diode, and pass through the support in order to be connected to the external electric connection members.
These connection pins are placed around the rear central part of the diode and are located on a circle of which the center is arranged substantially on the central axis of the diode. In the most frequent case, in which the diode comprises only two pins, the two pins are located on a circle of which the diameter corresponds to the segment connecting the two pins and of which the center is located on the central axis of the diode.
Generally speaking, the support on which the diode is arranged comprises a single substantially circular orifice through which the connection pins extend. The diode is then positioned in such a manner that its central axis is one and the same as the axis of the orifice. Furthermore, the diameter of the orifice is adjusted in order to allow the passage of the joining pins. The central axis of the diode then passes through the orifice into which the pins extend.
It has been observed, however, that the hottest spot of the diode is precisely in a central part located about the central axis of the diode. This arrangement thus means that the contact between the rear part of the diode located about the central axis and corresponding to this hot spot and the cooling means is therefore lost at the orifice through which the connection pins pass. This arrangement gives rise to a reduction in the capacity of the radiator to evacuate the heat generated by the diode, which increases the risk of damage to the diode from the excess heat produced.
Aware of this central hot-spot phenomenon, laser diode manufacturers have proposed placing the connection pins off center relative to the central axis of the diode so as to allow better contact between the cooling system and the rear central part where this hot spot is located. The connection pins are thus no longer arranged on a circle of which the center is placed on the central axis of the diode. Furthermore, when the diode comprises only two pins, the central axis of the diode no longer passes through the middle of the segment connecting the two pins or through this segment itself.
The use of this type of diode requires the diameter of the orifice through which the connection pins pass to be further enlarged in order to allow the rotation of the diode about its central axis. Moreover, the advantages arising from this new arrangement are lost insofar as, because the orifice is of larger diameter, the central part of the diode is even less able than before to evacuate the heat generated by the diode.